The present invention pertains to enclosures for delicate apparatus such as electronic equipment, sensitive measuring and/or recording devices, process control apparatus, electrical switching equipment or relays, and the like. More particularly, the present invention pertains to an enclosure that is durable, flexible and impervious, and which is thus highly reliable in protecting such apparatus against damage by being struck with solid objects, by contact with harmful liquids, gases or vapors, or by fire.
It is known that delicate apparatus of the aforementioned types should be adequately protected from physical and chemical damage, and prior enclosures for the purpose have comprised inner and outer plastic shells in spaced relation to each other and with a polymeric foam layer therebetween. In accordance with one known method, such enclosures have been produced by prefabricating the inner and outer shells from fiberglass reinforced polyester resin, followed by insertion of the inner shell into the outer shell and injection of a polymeric foam into the space between the two shells. In this method, the forming of the outer shell can present problems since it is necessary that a person work within the mold for laying up the fiberglass laminate. The laying up is usually done with the mold upside down so that the person is standing in a depression, and the quarters are not only cramped and difficult to work in, but often dangerous because it is difficult to provide good ventilation in such small spaces, and to provide access for quick escape of the person in case of an emergency.